In recent years, wind power generators have been used increasingly. The wind power generator which generates electric power through the use of natural wind is a favorable generator in that it has very little environmental effect. On the other hand, since the wind power generator uses uncertain natural wind as its motive energy, the output also depends on the uncertain wind, leading naturally to an unstable output. In order to stabilize the unstable output, consideration is being made of combination of the wind power generator with a storage battery.
However, it is still hard for the wind power generator combined with the storage battery to achieve the stabilization of the output to a system side to a satisfactory extent. Further, such a combination is undesirable in the aspect of system efficiency as well.
It is common that a threshold is preset so that when the output of the wind power generator exceeds the threshold, the storage battery is charged with the surplus electricity, while on the other hand, when the output of the wind power generation is less than the threshold, the shortage is supplemented by discharging electricity from the storage battery. However, the actual output of the wind power generator varies so widely that the storage battery is forced to recharge and discharge irregularly and unpredictably, thus making it hard to achieve the stabilization of the output to the system side to a satisfactory extent.
Take the redox flow battery combined with the wind power generator for instance: it is common that the redox flow battery prepared has a rated output equivalent to a rated output of the wind power generator. However, the output of the wind power generator varies irregularly in the order of from seconds to minutes, so that it often amounts to tens of percents of the rated output on an average. Thus, although the output to the battery to be recharged and discharged reaches the rating at a peak value, it amounts to tens of percents of the rated output on an average. The redox flow battery involves a power loss resulting from a pumping operation for circulating electrolytic solution, suffering from the disadvantage that when the pump is operated at a regular flow rate all the time, the power loss increases, leading to reduction of system efficiency.
Accordingly, it is a primary object of the present invention to provide an operating method of a redox flow battery system that can provide a stabilized output to a system from a redox flow battery system annexed to the wind power generator, to produce an improved battery efficiency.